[igorek]

I'd note again that the cable row is sometimes used to do back extensions (and to train the hamstrings), typically by keeping the arms straight and doing almost an RDL type of movement. For the purposes of training the back, the above right picture is an incorrect finishing position.

Moving around to behind the trainee, I want to show what it looks like from the back for the proper finish versus rounded shoulders position (shown two sets of pictures above). On the left, you can clearly see how the trainees shoulders are back and their shoulder blades are pulled together. On the right, the shoulders don't get pulled all the way back and the midback muscles aren't getting trained effectively. The trainee on the right needs to drop the weight and make sure that they get their shoulders blades pulled together at the end of every rep.

The next common error I want to show is a subtlety involving shoulder position. In the left picture below, the trainee (in addition to everything above) has scooped their shoulders down and back and is keeping the shoulders down. In the right picture (and this is a little tough to see; it's usually more exaggerated than this) the shoulders are hiking up towards the ears.

This tends to happen when the muscles which raise the shoulders (upper trapezius/levator scapulae) are tight and the muscle which keep them down (lower traps primarily) are weak. Stretching the traps/levator between sets and actively trying to scoop the shoulders down and back not only helps correct this flaw but also helps to rebalance the muscles that keep the scapulae in place.